Known are thermal, flow measuring devices, which have a sensor housing with two pin sleeves. Arranged in a first of these two pin sleeves is a heater, e.g. a heated resistance thermometer. Arranged in a second of these pin sleeves is a temperature sensor for ascertaining the temperature of the medium, which likewise can be embodied as a heatable resistance thermometer, which, however, in its operating state as a temperature sensor is not actively heated. By means of these two above-described sensor elements, a reliable flow measurement can occur.
For preventing measurement errors, it is expedient so to install the thermal, flow measuring device in a tube or pipe such that the flow of the measured medium, i.e. its flow direction, is perpendicular, thus at an angle of 90°, to a connecting axis, which is defined by the two pin sleeves. Therefore, the thermal, flow measuring device must be oriented very precisely, in order to avoid an angular offset from this ideal 90°-arrangement relative to the flow direction. This measurement error due to an angular offset is also referred to as the tilt angle sensitivity of a thermal, flow measuring device.
For lessening this tilt angle sensitivity, structural modifications were implemented in the product, t-mass 65 l, of the applicant. In the case of this construction, however, the installed position must be observed. The flow measuring device reliably ascertains the flow of a measured medium in a first flow direction and can compensate for an angular offset. There can, however, be situations, e.g. CIP-cleaning processes, rebounds of the measured medium or a controlled guiding of the measured medium in an opposite direction, which make a flow measurement in a second flow direction opposite to the first flow direction necessary. The property of a thermal, flow measuring device to be able to measure in the flow direction and in the opposite direction is referred to herein as bidirectionality.
A thermal, flow measuring device is additionally known from US 2015/0192442 A1. In this case, supplementally to the pin sleeves in FIGS. 1b and 2a two lateral, elongated elements are provided, which bring about a flow guidance. However, due to the flat nature of the elements elongated in parallel with the flow direction, the tilt angle sensitivity of the flow measuring device is only slightly improved.